Semiconductor device having a conductive layer with a cobalt tungsten phosphorus coating and a manufacturing method thereof

ABSTRACT

A semiconductor device capable of suppressing diffusion of copper at an interface between a copper wire and a cap film to enhance an electromigration resistance to ensure reliability of the copper wire, and a manufacturing method thereof are provided. The semiconductor device according to the present invention comprises an insulating film ( 12 ) formed on a substrate ( 11 ), a concave portion ( 13 ) (for example, a groove) formed in the insulating film, a conductive layer ( 15 ) embedded in the concave portion through a barrier layer ( 14 ), and a cobalt tungsten phosphorus coating ( 16 ) to connect with the barrier layer on the side of the conductive layer and to coat the conductive layer on the opening side of the concave portion.

TECHNICAL FIELD

The present invention relates to a semiconductor device and amanufacturing method thereof, and particularly, to a semiconductordevice having a conductive layer on which a cobalt tungsten phosphoruscoating is formed to serve as a cap on the conductive layer, and amanufacturing method thereof.

BACKGROUND OF THE INVENTION

Copper wires are of increasing importance in fine elements in whichdelays in circuits due to parasitic resistance and parasitic capacitanceof wires are dominant since the copper wires can achieve a lowerresistance, a lower capacitance, and higher reliability than those ofaluminum wires. As a typical method of forming copper wires, damasceneprocesses are widely accepted. Of the damascene processes, a dualdamascene process is accepted in view of manufacturing cost. With theemployment of this dual damascene process, it has been expected that acopper wire process would accomplish a lower cost than that of aconventional aluminum wire process.

However, since copper is prone to oxidization as compared with aluminum,it has been necessary to use silicon nitride (SiN) with a high relativedielectric constant of 8 as a cap film to prevent oxidization of thesurface of the copper. As a result, a detriment of increasing parasiticcapacitance in the overall wire system occurs. In addition, since thesurface of the copper is chemically unstable although the copper hasproperties which raise expectation of a high electromigrationresistance, an interface between the copper and the silicon nitride actsas a path on which the copper is preferentially diffused to cause aproblem of failing to obtain the expected high electromigrationresistance (reliability).

SUMMARY OF THE INVENTION

The present invention has been made to solve the aforementioned problemsand provides a semiconductor device and a manufacturing method thereof.

The semiconductor device according to the present invention comprises aninsulating film formed on a substrate, a concave portion formed in theinsulating film, a conductive layer embedded in the concave portionthrough a barrier layer, and a cobalt tungsten phosphorus (CoWP) coatingto connect with the barrier layer on the side of the conductive layerand to coat the conductive layer on the opening side of the concaveportion.

In the aforementioned semiconductor device, since the cobalt tungstenphosphorus coating is formed to connect with the barrier layer on theside of the conductive layer and to coat the conductive layer on theopening side of the concave portion, a cap layer on the conductive layeris formed of a material having conductivity. Also, since the cobalttungsten phosphorus coating is unlikely to serve as a path on whichcopper is preferentially diffused at an interface with the copper, ahigh electromigration resistance (reliability) can be obtained.

In addition, since the conductive layer is in a state in which it issurrounded by the barrier layer and the cobalt tungsten phosphoruscoating, the conductive layer is completely coated with and protected bythe barrier layer and the cobalt tungsten phosphorus coating even whenthe conductive layer is formed of a material prone to oxidization suchas copper. Furthermore, since the cobalt tungsten phosphorus coating isin close contact with the conductive layer on the top surface and theside surface closer to the top of the conductive layer, the cobalttungsten phosphorus coating is unlikely to come off. Consequently, thestrength of the connection of the cobalt tungsten phosphorus coatingwith the barrier layer is increased, so that the cobalt tungstenphosphorus coating and the barrier layer prevent diffusion of coppereven with the conductive layer made of copper and prevent diffusion ofoxygen to the conductive layer so as to prevent oxidization of theconductive layer.

The method of manufacturing a semiconductor device according to thepresent invention comprises the steps of forming a concave portion in aninsulating film formed on a substrate, forming a barrier layer on aninner surface of the concave portion and on a surface of the insulatingfilm and forming a conductive layer on the surface of the insulatingfilm to be embedded in the concave portion through the barrier layer,removing the conductive layer such that the conductive layer is left inthe concave portion and removing the barrier layer on the surface of theinsulating film such that the top end of the barrier layer left in theconcave portion is positioned between a side surface of the conductivelayer and a side wall of the concave portion, and forming a cobalttungsten phosphorus coating to connect with the barrier layer on a sideof the conductive layer and to selectively cover the conductive layer onan opening side of the concave portion with electroless plating.

In the aforementioned method of manufacturing a semiconductor device,since the barrier layer on the surface of the insulating film is removedsuch that the top end of the barrier layer left in the concave portionis positioned between the side surface of the conductive layer and theside wall of the concave portion, and the cobalt tungsten phosphoruscoating is then formed to connect with the barrier layer on the side ofthe conductive layer and to selectively cover the conductive layer onthe opening side of the concave portion, the cobalt tungsten phosphoruscoating is formed to connect to the barrier layer on the side of theconductive layer and to selectively cover the conductive layer on theopening side of the concave portion. Also, since the cobalt tungstenphosphorus coating is unlikely to serve as a path on which copper ispreferentially diffused at an interface with the copper, a highelectromigration resistance (reliability) can be obtained.

In addition, to remove the barrier layer on the surface of theinsulating film such that the top end of the barrier layer left in theconcave portion is positioned between the side surface of the conductivelayer and the side wall of the concave portion, a typical method ofremoving the barrier layer can be used. Specifically, at the typicalstep of removing the barrier layer formed on the surface of theinsulating film, over-etching is performed to completely remove thebarrier layer on the surface of the insulating film. Thus, the barrierlayer formed on the side wall of the concave portion is removed suchthat the top end thereof is closer to the bottom of the concave portionthan to the surface of the conductive layer. With this, when the cobalttungsten phosphorus coating is formed, it is formed to connect with thebarrier layer on the side of the conductive layer. Since the cobalttungsten phosphorus coating connects with the barrier layer on the sideof the conductive layer in this manner, the conductive layer is in astate in which it is surrounded by the barrier layer and the cobalttungsten phosphorus coating. Furthermore, since the connecting portionis located on the side of the conductive layer, the cobalt tungstenphosphorus coating is closely contact with the conductive layer on thetop surface and the side surface closer to the top of the conductivelayer, the cobalt tungsten phosphorus coating is unlikely to come off.Consequently, the strength of the connection of the cobalt tungstenphosphorus coating with the barrier layer is increased, so that thecobalt tungsten phosphorus coating and the barrier layer preventdiffusion of copper even with the conductive layer made of copper andprevent diffusion of oxygen to the conductive layer so as to preventoxidization of the conductive layer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic sectional view of a configuration showing anembodiment according to a semiconductor device of the present invention;and

FIGS. 2A to 2F are sectional views of manufacturing steps showing anembodiment according to a method of manufacturing a semiconductor deviceof the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment according to a semiconductor device of the presentinvention will be described with a schematic sectional view of aconfiguration of FIG. 1.

As shown in FIG. 1, an insulating film 12 is formed of, for example, asilicon oxide film, on a substrate 11. It should be noted that anorganic insulating film, a porous insulating film or the like can beused as the insulating film 12. A concave portion 13 formed of, forexample, a groove in which a groove wire is to be formed, is formed inthe aforementioned insulating film 12. A conductive layer 15 is embeddedin the concave portion 13 on inner walls thereof through a barrier layer14, bay way of example. The barrier layer 14 is formed of, for exampletungsten nitride, and the conductive layer 15 is formed of, for examplecopper or an alloy of copper. A cobalt tungsten phosphorus (COWP)coating 16 is formed to connect with the top end of the barrier layer 14on a side of the conductive layer 15 and to selectively coat theconductive layer 15 on an opening side of the concave portion 13. Inother words, the cobalt tungsten phosphorus coating 16 connects with thebarrier layer 14 on the side of the conductive layer 15, and the cobalttungsten phosphorus coating 16 and the barrier layer 14 surround theconductive layer 15.

While the concave portion 13 is formed of the groove in theaforementioned description, the concave portion 13 may be a connectinghole in which a plug for connecting one wire to another wire is to beformed, or a groove in which a wire is to be formed and a connectinghole formed on the bottom of this groove.

Since the cobalt tungsten phosphorus coating 16 is formed to connectwith the barrier layer 14 on the side of the conductive layer 15 and tocoat the conductive layer 15 on the opening side of the concave portion13 in the aforementioned semiconductor device, a cap layer on theconductive layer 15 is made of cobalt tungsten phosphorus havingconductivity. In addition, since the cobalt tungsten phosphorus coating16 is unlikely to serve as a path on which copper is preferentiallydiffused at an interface with the copper, a high electromigrationresistance (reliability) can be obtained.

In addition, since the conductive layer 15 is in a state in which it issurrounded by the barrier layer 14 and the cobalt tungsten phosphoruscoating 16, the conductive layer 15 is completely coated with andprotected by the barrier layer 14 and the cobalt tungsten phosphoruscoating 16 even when the conductive layer 15 is made of a material proneto oxidization such as copper. Furthermore, since the cobalt tungstenphosphorus coating 16 is in close contact with the conductive layer 15on the top surface and the side surface closer to the top of theconductive layer 15, the cobalt tungsten phosphorus coating 16 isunlikely to come off.

Consequently, the strength of the connection of the cobalt tungstenphosphorus coating 16 with the barrier layer 16 is increased, so thatthe cobalt tungsten phosphorus coating 16 and the barrier layer 14prevent diffusion of copper even with the conductive layer 15 made ofcopper and prevent diffusion of oxygen to the conductive layer 15 so asto prevent oxidization of the conductive layer 15.

Next, an embodiment according to a method of manufacturing asemiconductor device of the present invention will be described withsectional views of manufacturing steps of FIGS. 2A to 2F. Parts similarto those shown in FIG. 1 mentioned above are designated with the samereference numerals in FIGS. 2A to 2F.

As shown in FIG. 2A, a first wire 32, for example of a groove wireconfiguration, is formed through a barrier layer 32 b in a firstinsulating film 31 formed on a substrate (not shown). A diffusionpreventing layer 33 for covering the first wire 32 is formed on thefirst insulating film 31, and a second insulating film 34 is formedthereon. The diffusion preventing layer 33 may have a function as anetching stopper at the time of formation of a connecting hole. Inaddition, a third insulating film 35 is formed on the second insulatingfilm 34. A concave portion 36 (hereinafter described as a groove 36) isformed in the third insulating film 35, and a connecting hole 37 isformed to extend from the bottom of the groove 36, to pass through thesecond insulating film 34, and to reach the first wire 32.

A barrier layer 41 is formed on inner surfaces of the wire groove 36 andthe connecting hole 37 as configured above. The barrier layer 41 isformed of, for example, tungsten nitride. In addition, a copper seedlayer 42 is formed on the surface of the barrier layer 41 using adeposition technique such as sputtering. Typically, for a groove, aconnecting hole with a high aspect ratio, seed layer reinforcingelectrolytic plating is performed to supplement an insufficientthickness of a copper seed layer on a side wall of the groove, a sidewall of the connecting hole. In the figures, the copper seed layer 42for which the seed layer reinforcing electrolytic plating has beenperformed is shown. Then, the substrate is cleaned. This cleaning isperformed, for example, through washing.

Next, as shown in FIG. 2B, a conductive layer 43 made of copper isembedded in the groove 36 and the connecting hole 37 by performingcopper electrolytic plating. In this event, the conductive layer 43 madeof copper is also deposited on the barrier layer 41 on the thirdinsulating film 35. It should be noted that the copper seed layer 42 isshown as included in the conductive layer 43 in the figure. In thesequence of the electrolytic plating process, plating conditions areselected to planarize the surface of the conductive layer 43 after theplating to form a copper plating layer having a flat surface. Then, thesubstrate is cleaned. This cleaning is performed, for example, throughwashing.

Next, as shown in FIG. 2C, the substrate subjected to the aforementionedprocessing is annealed. This annealing promotes growth of copper crystalgrains in the conductive layer 43 having fine crystal grains after theelectrolytic plating.

Next, as shown in FIG. 2D, electrolytic polishing is performed to removethe conductive layer 43 on the surface of the insulating film (thirdinsulating film 35), leaving the conductive layer 43 only inside thegroove 36 and the connecting hole 37.

Subsequently, as shown in FIG. 2E, the barrier layer 41 made of tungstennitride is removed by wet etching with hydrogen peroxide. Specifically,an aqueous solution of the hydrogen peroxide is sprayed onto the surfaceof the substrate to dissolve and remove an unnecessary portion of thebarrier layer 41 made of tungsten nitride on the flat surface. Since theetching of the tungsten nitride progresses isotropically, over-etchingis required to some extent to completely remove the tungsten nitride onthe surface of the third insulating film 35. As a result, side etchingoccurs on the side wall of the groove 36, and a top end 41 t of thebarrier layer 41 is formed to be lower than a surface 43 s of theconductive layer 43. Then, the substrate is cleaned. This cleaning isperformed, for example, through washing.

Next, as shown in FIG. 2F, with electroless plating, a cobalt tungstenphosphorus (COWP) coating 44 is selectively formed on the exposedsurface of the conductive layer 43. For the selectivity of thedeposition, before the COWP electroless plating is performed, thesurface of the conductive layer 43 is coated with palladium byelectroless displacement plating of copper. This is because, with thepalladium coating, the deposition of the COWP is produced only on thepalladium using the palladium as a catalyst. Once the surface of thepalladium is coated with the COWP, plating growth of the COWP progressesthrough autocatalytic plating using the COWP itself as a catalyst withthe selectivity maintained. The exposed surface of the conductive layer43 due to the side etching produced by etching the barrier layer 41 madeof tungsten nitride is coated with this cobalt tungsten phosphoruscoating 44. Then, the substrate is cleaned. This cleaning is performed,for example, through washing.

Of the materials described in the aforementioned embodiment, the barrierlayer 41 is not limited to the tungsten nitride, and it may be replacedwith a material having similar functions, for example, tantalum nitrideor the like.

While the technique for forming the cobalt tungsten phosphorus coating44 on the conductive layer 43 formed of copper embedded in the groove 36has been described in the aforementioned description, application can bemade to a technique for forming a plug made of copper or an alloy ofcopper in a connecting hole and coating the top surface side of the plugwith a cobalt tungsten phosphorus coating, by way of example.

In the aforementioned method of manufacturing a semiconductor device,since the barrier layer 41 on the surface of the third insulating film35 is removed such that the top end of the barrier layer 41 left in theconcave portion (groove) 36 is positioned between the side surface ofthe conductive layer 43 and the side wall of the groove 36, and then thecobalt tungsten phosphorus coating 44 is formed to connect with thebarrier layer 41 on the side of the conductive layer 43 and toselectively coat the conductive layer 43 on the opening side of thegroove 36, the cobalt tungsten phosphorus coating 44 is formed toconnect with the barrier layer 41 on the side of the conductive layer 43and to selectively coat the conductive layer 43 on the opening side ofthe groove 36. In addition, since the cobalt tungsten phosphorus coating44 is unlikely to serve as a path on which the copper is preferentiallydiffused at the interface with the copper, a wire formed of theconductive layer 43 can achieve a high electromigration resistance(reliability).

In addition, the barrier layer 41 on the third insulating film 35 isremoved with the wet etching using the hydrogen peroxide. In this event,the over-etching is typically performed to completely remove the barrierlayer 41 on the surface of the third insulating film 35. Consequently,the top end of the barrier layer 41 left in the groove 36 is positionedbetween the side surface of the conductive layer 43 and the side wall ofthe groove 36. The barrier layer 41 formed on the side wall of thegroove 36 is removed such that its top end is closer to the bottom ofthe groove 36 than to the surface of the conductive layer 43. Thus, whenthe cobalt tungsten phosphorus coating 44 is formed, it is formed toconnect with the barrier layer 41 on the side of the conductive layer43. In this manner, since the cobalt tungsten phosphorus coating 44connects with the barrier layer 41 on the side of the conductive layer43, the barrier layer 41 and the cobalt tungsten phosphorus coating 44surround the conductive layer 43. Furthermore, since the connectingportion is located on the side of the conductive layer 43 to therebybring the cobalt tungsten phosphorus coating 44 into close contact withthe conductive layer 43 on the top surface and the side surface closerto the top of the conductive layer 43, the cobalt tungsten phosphoruscoating 44 is unlikely to come off. As a result, the strength of theconnection of the cobalt tungsten phosphorus coating 44 with the barrierlayer 41 is increased, so that the cobalt tungsten phosphorus coating 44and the barrier layer 41 prevent diffusion of the copper in theconductive layer 43. In addition, since diffusion of oxygen to theconductive layer 43 is prevented, oxidization of the conductive layer isprevented.

As so far described, according to the semiconductor device of thepresent invention, since the cobalt tungsten phosphorus coating isformed to connect with the barrier layer on the side of the conductivelayer and to coat the conductive layer on the opening side of theconcave portion, the interface between the cobalt tungsten phosphoruscoating and the conductive layer does not serve as a diffusion path ofcopper even when the conductive layer is formed of copper or an alloy ofcopper, so that electromigration resistance can be ensured. In addition,since the conductive layer is in a state in which it is surrounded bythe barrier layer and the cobalt tungsten phosphorus coating, theconductive layer can be completely coated with and protected by thebarrier layer and the cobalt tungsten phosphorus coating. Furthermore,since the cobalt tungsten phosphorus coating is in close contact withthe conductive layer on the top surface and the side surface closer tothe top of the conductive layer, the cobalt tungsten phosphorus coatingis unlikely to come off. From those facts, when the conductive layer isused as a wire or a plug, high reliability can be achieved. In addition,since a low dielectric constant insulating film can be directly formedon the cobalt tungsten phosphorus coating, wire parasitic resistance ofthe overall wire system is significantly reduced.

According to the method of manufacturing a semiconductor device of thepresent invention, since the barrier layer is removed such that the topend of the barrier layer left in the concave portion is positionedbetween the side surface of the conductive layer and the side wall ofthe concave portion, the cobalt tungsten phosphorus coating can beformed to connect with the barrier layer on the side of the conductivelayer and to coat the conductive layer on the opening side of theconcave portion in the subsequent process of forming the cobalt tungstenphosphorus coating. Thus, even when the conductive layer is formed ofcopper or an alloy of copper, since the interface between the cobalttungsten phosphorus coating and the conductive layer does not serve as adiffusion path of copper, electromigration resistance can be ensured. Inaddition, the cobalt tungsten phosphorus coating can be formed in astate in which the cobalt tungsten phosphorus coating and the barrierlayer surround the conductive layer, so that the conductive layer can becompletely coated with and protected by the barrier layer and the cobalttungsten phosphorus coating. Furthermore, since the cobalt tungstenphosphorus coating is formed in close contact with the conductive layeron the top surface and the side surface closer to top of the conductivelayer, the cobalt tungsten phosphorus coating is unlikely to come off.From those facts, when the conductive layer is used as a wire or a plug,a wire or a plug with high reliability can be formed. In addition, sincea low dielectric constant insulating film can be directly deposited onthe cobalt tungsten phosphorus coating, wire parasitic resistance of theoverall wire system can be significantly reduced.

1. A method of manufacturing a semiconductor device comprising the stepsof: forming a concave portion in an insulating film formed on asubstrate; forming a barrier layer on an inner surface of said concaveportion and on a surface of said insulating film and forming aconductive layer on the surface of said insulating film to be embeddedin said concave portion through said barrier layer; removing saidconductive layer such that said conductive layer is left in said concaveportion and removing said barrier layer on a surface of said insulatingfilm such that a top end of said barrier layer left in said concaveportion is between a side of said conductive layer and a side wall ofsaid concave portion; and forming a cobalt tungsten phosphorus coatingto connect with said barrier layer on the side of said conductive layerand to selectively cover said conductive layer on an opening side ofsaid concave portion with electroless plating.
 2. The method ofmanufacturing a semiconductor device according to claim 1, wherein: saidbarrier layer is made of tungsten nitride, and said barrier layer isremoved with wet etching using hydrogen peroxide.
 3. The method ofmanufacturing a semiconductor device according to claim 1, wherein: saidconcave portion is formed into a groove in which a wire is to be formed.4. The method of manufacturing a semiconductor device according to claim1, wherein: said concave portion is formed into a connecting hole inwhich a plug connecting one wire to another wire between layers is to beformed.
 5. A semiconductor device comprising: an insulating film formedon a substrate; a concave portion formed in said insulating film; aconductive layer embedded in said concave portion through a barrierlayer; a cobalt tungsten phosphorus coating to connect with said barrierlayer on a side of said conductive layer and to coat said conductivelayer on an opening side of said concave portion; said barrier layer isformed on a more inner side of said concave portion than said conductivelayer, and said barrier layer and said cobalt tungsten phosphoruscoating surround said conductive layer.